1. Field of the Invention
The present invention relates generally to a small lightweight refrigeration system and more specifically to such a system which dynamically controls the flow of working fluid within the system in a manner which enables the unit to be rendered both light weight and highly compact.
2. Related Art
In order to render refrigeration units small and compact efforts have been directed to rendering the pump, which is used to compress and drive the working fluid through the system, small, compact and quiet. However, these arrangements have not met with the full success in that they inevitably rely on rotating type pumps or compressors and tend to become quite complex and therefore expensive. One example of a compact device which uses pistons to achieve cooling, although it is directed to a very special type of cryogenic application, is found in U.S. Pat. No. 4,858,442 issued on Aug. 22, 1989 in the name of Stetson.
However, irrespective of such developments, still problems remain in the type of refrigeration system which is incorporated into air conditioning units such as those used in automotive vehicles. For example, in such arrangements, the compressor is invariably driven by the output of the prime mover, viz., the engine, and is therefore located in the engine compartment close to the engine to enable the appropriate drive connection (usually a belt drive) to be established. This disposition, along with the need to have other pieces of apparatus such as the condenser located close the compressor and disposed in similar locations, leads to a number of drawbacks.
More specifically, the fact that the compressor is driven by a mechanical connection with the engine demands that its rotational speed will vary and thus requires that the air-conditioning system be provided with an accumulator or some form of compensation arrangement, in order to compensate for the fluctuations in the amount of refrigerant which is discharged by the compressor. Furthermore, the fact that the compressor tends to be disposed in a heated environment (viz., in a hot engine compartment and close to an even hotter engine) exposes the coolant to additional heating which demands the use of thick, robust and expensive thermally insulated hoses, and also requires that the condenser be located at some distance from the compressor so as to escape the heat radiation to much as possible and to be exposed to a flow of cool air. However, the conduiting which is associated with the condenser usually must pass through the engine room or close thereto, on its way to the evaporator, and therefore must also be thermally insulated in order prevent it from becoming excessively reheated.
Furthermore, a considerable length of conduiting is involved which, in combination with the need to provide the above mentioned accumulator, causes the total amount of working fluid which is required, to increase. The pumping loads involved in pushing the refrigerant (i.e., the working fluid) through the long conduits in addition to the weight of the materials and apparatus involved, leads to a situation wherein automotive air conditioning systems are inevitably heavier, more complex, more expensive and less efficient than desired.
In high performance vehicles, wherein the distribution of heavy/bulky elements such as the compressor and the condenser is becoming ever more important due to the use of advanced/expensive materials which allow the weight of various components of the vehicle/engine to be reduced, the need to have the compressor, etc, disposed in the highly cramped engine compartment, becomes even a greater problem. Not only is the weight distribution rendered more difficult, but the presence of such devices tends to reduce the ability to add further equipment such as a second turbo-charger or intercooler.
To make matters worse, with the approach of electrically powered vehicles, which use fuel cells and or hybrid generation systems, the availability of a powerful prime mover such as the internal combustion engines which are in current use, will vanish and the need for lighter, more power efficient arrangements will increase exponentially.
Thus, as will be appreciated, there is a need for a light, power economical refrigerating arrangement which can overcome the above mentioned types of drawbacks as well as provide a quite and compact arrangement which can be conveniently located as needed.